What is Sensitive Plant Herb Extract ? The sensitive plant is popular in cultivation around the world, and is enjoyed by many as a curiosity due to its highly touch-sensitive leaves. Robert Hooke (English scientist famous for his microscopy work, 1635-1703) was one of the first people to investigate the movements of Mimosa pudica, and at that time it had been suggested that plants had nerves and tissues similar to those in animals. It was later discovered that the leaves fold as a result of the internal movement of water, and the mechanics of the process are now well-documented. A stimulus, such as touch or air movement, triggers certain areas of the stem to release chemicals, which cause water to move out of cell vacuoles and leads to cell collapse. This rapid plant movement is thought to act as a defence against herbivores, which may be deterred by the dramatic response, or if they are small, may be dislodged as the leaves collapse.